package per.jdz.unsafe;

import java.util.Collections;
import java.util.HashSet;
import java.util.Set;
import java.util.UUID;
import java.util.concurrent.CopyOnWriteArraySet;

// HashSet底层是HashMap
public class SetTest {
    public static void main(String[] args) {
//        Set<String> set = new HashSet<>();
//        Set<String> set = Collections.synchronizedSet(new HashSet<String>());
        CopyOnWriteArraySet<String> set = new CopyOnWriteArraySet<>();
        for (int i = 0; i < 20; i++) {
            new Thread(()-> {
                set.add(UUID.randomUUID().toString().substring(0, 5));
                System.out.println(set);
            }, String.valueOf(i)).start();
        }
    }
}
